如何使用反射访问地图的nil键？

Question

I have a map that has a nil-keyed value:

mapp := map[interface{}]interface{}{
    nil: "a",
}

Accessing it's nil key's directly works:

fmt.Println("key[nil]:", mapp[nil])

But using reflection it doesn't - how to do this?

rmapp := reflect.ValueOf(mapp)
rkey := reflect.ValueOf(interface{}(nil))
rval := rmapp.MapIndex(rmapp.MapIndex(rkey))
fmt.Println("key[nil]:", rval)

Non-working code here:
https://play.golang.org/p/6TKN_tDNgV

Answer 1

The missing piece appears to have been the zero value of the map's key type, which is needed to access the nil key of the map.

refmap.MapIndex(reflect.Zero(refmap.Type().Key()))

playground example